The present invention relates to a method and arrangement for aeration of liquids, particularly for aerobic growing of microorganisms.
Methods and arrangements for aeration in the processes of growing microorganisms are known in the art. Agitating devices or stirrers with an upper drive and a lower drive have been found suitable for rotation of liquid volumes of up to 300 m.sup.3. For rotation of larger liquid volumes in closed containers air is supplied through the bottom of the containers under pressure. Thereby, rotation of the container contents, in accordance with the principle of the air-lift-pump is performed. The known methods and arrangements possess the disadvantages in that in the case of large volumes the mechanical agitation by agitating devices results not only in high energy consumption but also in that the upper drive devices require very long shaft, and the lower drive devices cause sealing problems because of high hydrostatic pressure. When fermenters operating in accordance with the air-lift-pump principle are utilized, it is necessary to provide compressors of great sizes in order to supply compressed air. By no means, however, the homogeneity can be guaranteed in large liquid volumes.
The Swiss Pat. No. 572,978 discloses an arrangement which has a horizontally located container including several rotary devices which are connected with each other in series. Each block forms a unit in a common container. This fermenter is satisfactory with respect to withdrawal of heat, however, it has the disadvantage in that dead zones take place in the regions of not exactly defined limiting faces between two neighboring aeration units.